With modern signal processing and telecommunication technology, target audio signals and background signals can be separated into multi-channel signals, or different signals in different directions or locations (such as different points in a room, or different signals from different cities) can be taken separately, mixed and transmitted to remote listeners. Current solution renders multi-talker speech sounds in different horizontal directions and mixes multi-channel speech signals into left and right channels so that listeners in the receiver side via stereo headphones or loudspeakers can perceive the locations of different speakers and understand desired speakers even if multiple people are talking simultaneously.
While more and more users have adopted stereo headphones or multi-channel sound reproduction systems to benefit from such spatialized speech communications, there are still a large number of users listening to sounds through mono-channel sound devices such as BlueTooth headsets and telephones. It is desirable to provide monoaural device users with the cues to separate different sound signals and understand the speech from target speakers among multiple simultaneous audio signals.
Even for listeners with multi-channel playback devices, if the original audio signal is created without spatial cues, or if multiple sound signals originate from almost the same position, it is desirable to provide the listeners with more cues to distinguish different sound signals.